1. Field of the Invention
The present invention relates to a vehicular electronic key system.
2. Discussion of the Background
There is a known method that allows the owner of a vehicle to set, in an electronic key (so-called “smart key”), a mode in which specific functions of the vehicle are limited, these functions being permitted with use of the electronic key (so-called “valet mode”) and provide a person other than the vehicle's owner with the electronic key when this person drives the vehicle.
There is a system improves such system (e.g., see Japanese Unexamined Patent Application Publication No. 2006-225976). According to this system, for example, an electronic key includes a portable unit (key body), a mechanical key and a tongue, and transmits a state signal indicative of the attachment/detachment state of the tongue to/from the key body to a vehicle, and an on-vehicle control unit sets a valet mode when the state signal received from the electronic key indicates detachment of the tongue.
Since the owner of the vehicle entrusts another person with the key body having only the tongue removed from the electronic key and the mechanical key in the system according to the related art, this person can unlock doors and start the engine with the mechanical key even when the battery of the key body is dead.